The present invention relates to a grid moving apparatus arranged in a radiographing apparatus for irradiating an object with X-rays.
For example, in an x-ray diagnostic apparatus for diagnosing a patient upon irradiation of X-rays, a grid is arranged in front of a film for recording an X-ray image to control the incident X-ray on the film. In the X-ray radiographing mode, scattering X-ray beams are generated from the object when X-rays have passed through the object (patient). If the scattered X-ray beams are incident on the film, the contrast and quality of a resultant radiograph are degraded. Therefore, the scattered beams are eliminated by the grid in the X-ray radiographing mode.
Such a grid is formed by alternately arranging segments (e.g., lead) which do not pass X-rays and other segments (e.g., hole, wood, paper, aluminum and the like) which pass X-rays. With this structure, the grid permits transmission of a direct X-ray beam passed through the object, and inhibits transmission of scattered beams from the object.
However, since the segments form a grid pattern, if the grid is fixed in position, a grid pattern image may be formed on the film. For this reason, a swing mechanism is coupled to the conventional apparatus swinging the grid, thereby forming no grid pattern image on the film.
X-rays passed through the object are partially eliminated by the grid. Therefore, X-rays of a relatively high does are to be irradiated from an X-ray tube. However, when joints are to be imaged or when the patient is a child, X-rays of a low dose are projected in order to prevent adverse influence of the X-rays on the body. In this case, the grid must be removed from an X-ray imaging position.
Therefore, both mechanisms for swinging the grid and for selectively removing it from the imaging position are required.
Although they can be simply combined, this results in a complicated, bulky grid moving apparatus.